The evaluation of the state of polarization of light received from an object has many applications. For example, polarization based analysis provides information on the orientation in space of chemical bonds, surface orientation, refractive index, texture (including orientation of surface texture), and roughness. Polarization can be used in applications such as the visualization of mechanical stresses and the evaluation of products ranging from surface coatings to liquid crystal displays. Other applications include haze and glare reduction in photography, as well as deepening the apparent color of the sky.
The determination of the state of polarization of an optical beam or other optical signal typically requires two or more measurements. For example, the state of polarization of a partially polarized optical beam can be determined with three polarization based measurements along with measurement of total beam intensity. This series of measurements must be carefully executed to avoid inducing polarization changes in the optical beam. Measurement systems that implement such measurements, perform data reduction, and report Stokes vectors, Mueller matrices, Jones vectors, or other polarization parameters are generally referred to as polarimeters. Polarimeters commonly incorporate motors and/or beamsplitters, and tend to be bulky and expensive.
So-called “imaging polarimeters” can provide images based on the state of polarization of an optical flux received from an object being imaged. Imaging polarimetry faces the many of the same difficulties as non-imaging polarimetry as well as additional problems. For example, the acquisition of multiple polarizer measurements for each image pixel can be slow, and object motion or changes in object illumination can impair image accuracy or introduce image blur. In one approach to imaging polarimetry, an array of micropolarizers is situated near a focal plane array so that each pixel of the focal plane array receives an optical flux associated with a state of polarization defined by one of the micropolarizers. Examples of such systems are described in Gruev et al., U.S. Patent Application Publication 2007/0241267 and Mattox et al., U.S. Patent Application Publication 2008/0165359, both of which are incorporated herein by reference. Signals from several pixels of the focal plane array can then be combined. Unfortunately, conventional approaches to combining these signals not only reduce image resolution but mix polarization measurements from different object locations. Thus, a lower resolution image with polarization artifacts is produced.